Process for producing cyanoalkylsilanes



2,906,765 .PROCESS FOR PRODUCING CYA'NOALKYL- S'ILANES VictorB. Jex and John McMahon, Buifalo,N.Y., as-

signors to Union Carbide "Corporatiop, a corporation of New York N Dra ng. Application; December 23, 1-955 Sfl' a N 1 2 31 1 15 Claims. ((31; 260-4483) invention relates to aprocessfor producing cyanoallr-ylsilanes. More particularly, theinvention relates to aprocess for producing cyanoalkylsilanes. containing at least one hydrolyzable group bonded to the silicon atom here f.

By reacting an olefinic nitnle .of the type represented by ,acrylonitrile, methacrylonit-rile, crotononitrile and the, like with a silane containing at least one-hydrogen atom and at least one hydrolyzable group bonded to silicon atom thereof there is produced a .reaction product from which an alpha-cyanoalkylsilane can be recovered; The oyera-ll reaction which .-takes place can be graphicallyrepresented by the following equation, which depicts, for the purpose of illustration, the reaction between acrylonitrile and trichlorosilane.

The present invention is based on o r discovery that an olefinic nitrile or alkene nitrileof thetype represented by acrylonitrile, methacrylonitrile,crotononitrile-and the like can "be caused to react with a silane, -containing atleast one hydrogen atom and at least one hydrolyzable group bonded to the silicon atQur'thereof, in the presence of a catalyst to produce a beta-cyanoalkylsilane by the addition of a silylgroup ,to the, .beta carbon atom of :such nitrile, that is the olefinic carbon atom furtherrernoved from the cyano. group of the nitrile, and-by'theaddition of a hydrogen atom to the alphacarbon atom of such nitrile, that is the vicinal olefinic carbon atom. Based .on our discovery we have further found that any olefinic nitrile can :be caused toreact with a .silane, containingat least one thydrogenatomyand atleast one hydrolyzable group bonded to the-silicon, gatom thereof, in the presence of a catalyst to produce a cyanoalkylsilane by the addition of a silyl group to the olefinic carbon atom further removed from the cyano group of the (mor Qu rr ess-can be c ie to t-hyfq vmin a mixtur of an l fi i u' a i an c ntai in atsls s r n r dwseaat m. n -a lea mu htdrsly ehl t muribgrd d- Patented Sept. as, reap 2-. to the silicon atom thereof and a-sma-ll or catalytic amount of a phosphonate as a catalyst for the reaction andheatf ing the mixture to a temperature sufiiciently elevated to cause the starting materials to react. There results or is'produced a cyanoalkylsilane by the addition of silyl group to the olefinic carbon atom of the nitrile further removed from the cyano group'aud by the addition of a hydrogen atom to the olefinic carbon'at'om of the nitrile closer to the cyano group. i i

The silane starting materials, containing at least one. hydrogen atom and at least one hydrolyzable group bonded to the silicon atom thereof, which we can employ in our process can be graphically represented by' the following general formula:

wherein E represents a hydrogen atom or a hydrocarbyl group, preferably a saturated aliphatic hydrocarbyl group as for example, an alkyl group, such as methyl, ethyl, propyl, butyl, pentyl and the like; a cycloalkyl groupsuch as cyclopentyl, cyclohexyl, methylcyclopentyl, ethylcyclohexyl, and the like; or an aryl group such 'as naphthyl, tolyl, methylnaphthyl and the like, X is a hydrolyzable group such as a halogen atom, preferably a chlorine atom or a hydrocarbyloxy group, preferably an a-lkoxy or an aryloxy group such as methoxy, ethoxy, propoxy,

phenoxy and the like, and n is a whole number having a value of from 0 to 2. Illustrativeof the silane starting materials are trichlorosilane, triethoxysilane, dichloro-- silane, diethoxysilane, monochlorosilane, monoet-hoxysilane, methyldichlorosilane, ethyldiethoxysilane, diethylethoxysilane,dimethylchlorosilane, butylet'hylchlorosilane, phenyldichlorosilane, phenylethylethoxysilane, dipropylphenoxysilane and the like.

The olefinic nitrile starting materials which We can employ in our process are the acyclic aliphatic monoolefinic nitriles which contain from three to ten carbon atoms to the molecule. Illustrative of such olefinic nitriles or alkene nitriles are acrylonitrile, methacrylonitrile, allyl cyanide, 1-cyano-3- butene, -1-cyano-4 -'p entene, l-cyano-I-hexene and the like. Gur preferred olefinic nitrile starting materials are those compounds in which the unsaturated grouping is. directly .bondedithrough one of the carbon atoms thereof--- to the carbon atom of the cyano group. Such olefinic nitriles. are commonly known as thevinyl-typecyanid'es and can be represented graphically by the general'forrnula:

wherein R can be a-hydrogenatom or an alkyl group'as:

for example methyl, ethyl, propyl, ,butyl and the like and A is either a hydrogen atom or .a methyl group. Illustrative of such vinyl-type cyanides are acrylonitrile, methacrylonitrile, crotononitrile, and the like.

The phosphonate compounds which we employ as catalysts in, our process direct the addition of the .silyl group of our starting ,silanerto the olefinic carbon atom of our starting nitrile further removed from the cyano.

, for. examplealkyb. cycloalkyl or aryl grgupsmhicheneed,

not necessarily be the same. Illustrative of such groups are methyl, ethyl, propyl, butyl, pentyl, cyclohexyl, phenyl, tolyl and the like. The phosphonates which we prefer to employ in carrying out our process are: diethyl ethane phosphonate, dibutyl butane phosphonate and diphenyl benzene phosphonate.

We have found that the amount of the catalyst employed in our process is not narrowly critical. Thus, amounts of the phosphonate compounds from as little as about 0.2 parts to as much as about parts by weight per 100 parts of the total weight of the starting materials can be favorably employed. We preferably employ the catalyst in an amount of from about 0.3 parts to about 3 parts by weight per 100 parts of the total weight of the nitrile and silane starting materials. Amounts of the phosphonate compounds in smaller or greater quantities than the favorable range can also be employed. However, no commensurate advantage is obtained thereby.

The olefinic nitrile and silane starting materials can be employed in our process in amounts which can vary from about one-half to 2 moles of the nitrile per mole of the silane. Preferably the reactants are employed in equimolar amounts. Amounts of either of the starting materials in excess of the ratios set forth above can also be employed; however, no commensurate advantage is obtained thereby.

To facilitate observation and at the same time to favor closer control of the reaction conditions, most of our experimental work was carried out in pressure vessels or bombs, with agitation being provided if desired by continuous shaking. Similar results can be obtained with flowing reactants in apparatus of known design permitting the maintenance of a closed system. In the reactions with which our invention is concerned, it is desirable to maintain sufliciently high concentrations of the reactants (as measured for example in moles per liter of reaction space) to promote effective contact between the molecules to be reacted. When one of the reactants is a gas, or a liquid readily volatile at the reaction temperature, and the reaction mixture is permitted to expand freely on heating, the concentration of that reactant will fall to a low value thus considerably slowing the reaction rate. If, however, the reactants are charged to a closed vessel which is sealed before heating, the initial concentration of any reactant falls off through its consumption by the reaction. If a reactant is a gas, it may be desirable to charge the reaction vessel to a considerable pressure to secure an adequate concentration and reaction rate, and also to supply enough of the reactant to produce an acceptable quantity of the product.

The temperatures which can be employed in carrying out our process are not narrowly critical and can vary over a wide range. For example, temperatures as low as 40 C. and as high as 350 C. can be advantageously employed. When conducting the process of the invention in a closed vessel a temperature in the range from about 125 C. to about 250 C. is preferred. Under such conditions a reaction period of from about two to about five hours is suitable. Temperatures of from about 175 C. to about 300 C. are preferred when conducting the process in apparatus which provides for the flow of the reactants and products while maintaining the conditions of a closed system. In such systems, where the pressure may range from atmospheric up to 4000 pounds per square inch and higher, the timerequired for the reaction to take place can be as short as 0.005 minutes.

In carrying out the process of our invention theproduct initially obtained comprises a mixture of compounds including the main cyanoalkylsilane reaction product as well as some unreacted nitrile and silane starting compounds. The desired addition product, formed by the addition of a silyl group to the olefinic carbon atom of the nitrile further removed from the cyano group and by the addition of a. hydrogen atom to the olefinic carbon ato'm closer to the cyano group, which contains at least one hydrolyzable group bonded to the silicon atom thereof, as for example beta-cyanoethyltrichlorosilane, can be recovered from the initially obtained reaction product by a distillation procedure which is preferably conducted under reduced pressure.

The mechanism of our overall reaction whereby products are produced by the addition of a silyl group to the olefinic carbon atom of the starting nitrile further removed from the cyano group and by the addition of a hydrogen atom of the olefin carbon atom of the starting nitrile closer to the cyano group with the apparent suppression of other addition or reaction products is not known with certainty or fully understood. It is known that upon heating our reactants in the absence of a phosphonate other reactions take place such as: the formation of both siliconand non-silicon-containing free radicals and complexes, the homopolymerization of the starting nitrile, and even the disproportionation of the starting silane has been observed. In addition, it is known that in the absence of a phosphonate as catalyst, our preferred starting materials can react to produce a product from which an alpha-cyanoalkylsilane, formed by the addition of a silyl group to the olefin carbon closer to the cyano group and by the addition of a hydrogen atom to the vicinal olefinic carbon, can be recovered with no beta addition products being formed. One possible explanation for the course which our reaction follows when a silane and an olefinic nitrile react in the instance where the nitrile is a vinyltype cyanide is that the addition of the silyl group to the olefinic carbon atom further removed from the cyano group of the nitrile occurs through an ionic mechanism while the addition of such silyl group to the olefinic carbon atom closer to the cyano group of the nitrile occurs through a free radical mechanism. If such is the case, then the activation energy required for the reaction, between our starting nitriles and silanes, to proceed by a free radical mechanism is considerably less than that required to cause the reaction to proceed by an ionic mechanism and consequently the reaction between an olefinic nitrile and a silane, as for example acrylonitrile and trichlorosilane will produce the alpha-addition product, namely, alpha-cyanoethyltrichlorosilane. On the other hand, our phosphonate catalysts apparently have the effect of markedly decreasing the activation energy required for the reaction to proceed by an ionic mechanism and therefore when employed in such reactions, as for example in the above acrylonitrile trichlorosilane reaction, result in the production of beta-cyanoethyltrichlorosilane.

When the olefinic nitrile is of the type represented by allyl cyanide, that is where the unsaturated grouping is removed by one or more carbon atoms from the cyano group, our catalyst also functions in promoting the reaction thereof with our silane starting materials to produce addition products by the addition of a silyl group to the olefinic carbon atom more removed from the cyano group, and by the addition of a hydrogen atom to the olefinic carbon closer to the cyano group. By way of illustration, gamma-cyanopropyltrichlorosilane is prepared by reacting allyl cyanide with trichlorosilane in the presence of a phosphonate catalyst in accordance with the subject process.

Bis(cyanoalkyl)silanes are produced in the practice of the process of our invention when our starting nitriles are reacted with silanes containing at least two hydrogen atoms bonded to the silicon atom thereof. In such instances the nitrile starting material is preferably employed in an amount of at least twice the number of moles of the starting silane. The products of the reaction include, in addition to the desired bis compound, the cyanoalkylhydrogen silane. By way of illustration, when two moles of acrylonitrile are reacted with one mole of dichloro- .perature of 200 C. for a period of two hours.

To a 50 cc. steel pressure vessel were added 0.15 moles (7.9 g.) of acrylonitrile, 0.15 moles (20.3 g.) of trichlorosilane and 0.56 g. (2% by Weight) of diphenyl benzene phosphonate. The vessel was sealed and heated to a tem- After heating, the vessel was cooled to room temperature and 23 g. of product removed therefrom and placed in a flask connected to a distillation column. The contents of the flask were heated to its boiling temperature under reduced pressure and there was obtained 14.34 g. of beta-cyanoethytrichlorosilane boiling at a temperature of 75 to 80 C. under a reduced pressure of 3 mm. Hg. The 14.34 g. of beta-cyanoethyltrichlorosilane represented a yield of 50.7 percent based on the total number of moles of the starting materials.

Example 2 To a 50 cc. steel pressure vessel was added 0.15 moles (7 .9 g.) of acrylonitrile, 0.15 moles (20.3 g.) of trichlorosilane and 0.5 6 g. (2 percent by weight) of dibutyl butane phosphonate. The vessel was sealed and heated to a temperature of 200 C. for a period of two hours. After heating, the vessel was cooled to room temperature and the 24.3 g. of product removed therefrom and placed in a flask connected to a distillation column. The contents of the flask were heated to its boiling temperatures under a reduced pressure and there was obtained 11.76 g. of beta-cyanoethyltrichlorosilane. Beta-cyanoethyltrichlorosilane was identified by infra-red spectrum analysis. The 11.76 g. of beta-cyanoethyltrichlorosilane represented a yield of 41.6 percent based on the total number of moles of the starting materials.

Example 3 To a 50 cc. steel pressure vessel was added 0.15 moles (7.9 g.) of acrylonitrile, 0.15 moles (20.3 g.) of trichlorosilane and 0.56 g. (2 percent by weight) of diethyl ethane phosphonate. The vessel was sealed and heated to a temperature of 200 C. for a period of two hours. After heating, the vessel was cooled to room temperature and the 22.4 g. of product removed therefrom and placed in a flask connected to a distillation column. The contents of the flask were heated to its boiling temperature under a reduced pressure and there was obtained 11.72 g. of beta-cyanoethyltrichlorosilane. Beta-cyanoethyltrichlorosilane was identified by infra-red spectrum analysis. The 11.72 g. of beta-cyanoethyltrichlorosilane represented a yield of 41.5 percent based on the total number of moles of the starting materials.

Example 4 To a 50 cc. steel pressure vessel were added 0.15 mole (7.9 g.) of acrylonitrile, 0.15 mole (20.3 g.) of trichlorosilane and 0.56 g. (2 percent by weight) of diphenyl benzene phosphonate. The vessel was sealed and heated to a temperature of 200 C. for a period of two hours. After heating, the vessel was cooled to room temperature and the product removed therefrom and placed in a flask connected to a distillation column. The contents of the flask were heated to its boiling temperature under reduced pressure and there was obtained 12.13 g. of beta-cyanoethyltrichlorosilane boiling at a temperature of 75 to C. under a reduced pressure of 3 mm. Hg. The 12.13 g. of beta-cyanoethyltrichlorosilane represented a yield of 43.0 percent based on the total number of moles of the starting materials.

What is claimed is:

1. A process for reacting a silane, represented by the formula:

where E represents a member of the group consisting of hydrogen and a hydrocarbyl group, X represents a hydrolyzable group from the class consisting of halogen and hydrocarbyloxy groups and n represents a whole number having a value of from 0 to 2, with an alkene nitrile to produce a cyanoalkylsilane by the addition of a silyl group to the olefinic carbon atom of said alkene nitrile further removed from the cyano group thereof and by the addition of a hydrogen atom to the olefinic carbon atom of said alkene nitrile closer to the cyano group thereof which comprises forming a mixture of said silane, said alkene nitrile, and a hydrocarbyl phosphonate catalyst, heating said mixture to a temperature of at least 40 C. to cause said silane and nitrile to react to produce a cyanoalkylsilane by the addition of a silyl group to the olefinic carbon atom further removed from the cyano group of the starting nitrile and by the addition of a hydrogen atom to the olefinic carbon atom closer to the cyano group of the starting nitrile.

2. A process for reacting a silane, represented by the formula:

hydrogen and a hydrocarbyl group, X represents a hydrolyzable group from the class consisting of halogen and hydrocarbyloxy groups and n represents a whole number having a value of from 0 to 2, with an alkene nitrile containing the unsaturated grouping to produce a cyanoalkylsilane by the addition of a silyl group to the carbon atom of said unsaturated grouping further removed from the cyano group of said nitrile and by the addition of a hydrogen atom to the carbon atom of said unsaturated grouping closer to the cyano group of said nitrile which comprises forming a mixture of said silane. said nitrile, and a hydrocarbyl phosphonate catalyst, heating said mixture to a temperature of from about 40 C. to about 350 C. to cause said silane and nitrile to react to produce a cyanoalkylsilane by the addition of a silyl group to the carbon atom of the unsaturated grouping more removed from the cyano group of the starting nitrile and by the addition of a hydrogen atom to the carbon atom of the unsaturated grouping closer to the cyano group of the starting nitrile and recovering said cyanoalkylsilane.

3. A process for reacting a silane represented by the formula:

where E represents a member of the group consisting of hydrogen and a hydrocarbyl group, X represents a hydrolyzable group taken from the class consisting of a halogen and hydrocarbyloxy groups and n represents a whole number having a value of from 0 to 2, with a nitrile of the formula:

1 RCH=OON where R is a member of the group consisting of hydrogen .and an alkyl group and A vis a member of the group consisting of a hydrogen atom and a methyl group to produce a cyanoalkylsilane by the addition of a silyl group torthe olefinic carbon atom of the nitrile further removed from the cyano group thereof and by the addition of a hydrogen atom to the, olefinic carbon atom of the nitrile closer to the cyano group thereof which comprises forming a mixture of said silane, nitrile, and a hydrocarbyl phosphonate catalyst free of aliphatic unsaturation, heating said mixture to a temperature of from about 40 C. to about 350 C. .to cause said silane and ,nitrileto react to produce a cyanoalkylsilane by addition ofjaisilylgroup to the olefiniccarbon atom further re- .moved from the cyano group of the starting nitrile and by the addition of a hydrogen atom tothe olefiniccarbon atorn ofthegnitrile closer to the cyano group thereof and recovering said cyanoalkylsilane.

4. A process for producing a beta-cyanoethylsilane which comprisesforming arnixture comprising a silane, of the formula:

where E represents a member of the group consisting of hydrogen and a hydrocarbylgroup, X represents a hydrolyzable group taken from the class consisting of a .halogen and hydrocarbyloxy groups and n represents a wholenumber having a value,of;from to 2, acryloni- Mile and a hydrocarbyl phosphonate catalyst, heating said mixture to a temperature sufficiently elevated to beta-cyanoethylsilane.

5. A process for producing a beta-cyanoethylsilane which comprises forming a mixture comprising a silane of the formula:

,cause saidsilane andacrylonitrile to react to produce a .Where E represents amember of the group consisting of .hydrogen and a:hydrocarbyl .group, X represents a hydrolyzable group takenifrom the class consisting of a halogen and hydrocarbyloxygroups and n represents a whole number having a value-of from 0 to 2, acrylonil e wlmq r u ph spho te cata y heating said mixture to.a,.temperatureof-fromabout 125 C. to. about 300 C. to causesaid silane .and acrylonitrile to;r.eact to produce .a betacyanoethylsilane and recovering fsaid beta-cyanoethylsilane. A .process for producing a gamma-cyanopropylsilane-which comprises forminga mixture comprising a ,silaneof the. formula:

l tn) H- a-n) silane to react to produce beta{cyanoethyltrichloro silane.

8. A process for producing beta-cyanoethyltriethoxysilane which comprises forming a mixture comprising acrylonitrile, triethoxysilane and-a hydrocarbyl phostriehlorosilaneand a dibutyl butane phosphonate, heating said mixtureto a-temperature of from about-125 C. -to about 300 C.- to cause said acrylonitrile and ,phonate,.heating saidmixture to atemperature of trom about 1C. to about 300 C. to cause said acrylonitrile and triethoxysilane to react to produce beta -cyanoethyltriethoxysilane.

"9. A' process for producing -beta -eyanoethyltrichlorosilane .which comprises forming a .mixture comprising acrylonitrile, .trichlorosilane and diphenyl .benzene phos- I phonate, heatingsaidmixture to a temperature of from about 125 .f C. to about 300 C. to causesaid acrylonitrile and trichlorosilane to reactto produce beta-cyanoethyltrichlorosilane.

10. A process for I producing beta-cyanoethyltriethoxysilane which comprises forming a mixture comprising acrylom'trile, triethoxysilane and diphenyl benzene phosphonate, heating said mixture to a temperature of from about- 125 C.-to about 300 -C.'to cause said acrylonitrile and triethoxysilane .to reactto produce beta-cyanoethyltriethoxysilane.

-A-process for producing -beta cyanoethyltrichlorosilane whichcomprises forming a mixture of acrylonitrile,

triehlorosilane 'to react to produce-beta'cyanoethyltri- :ehlorosilane.

'12. A- process for producingbeta-cyanoethyltrichlorosilane which comprises forming a mixture of acrylonitrile, -triehloro'silaneand .a diethyl ethane phosphonate,- heat- -ing"said mixture-t0 a'temperature of from.about.125 C.

to about 300 C. to cause said acrylonitrileand trichlorosilane to react to producebeta-cyanoethyltrichlorosilane.

-3- t' r w fis z roduei t r t syen th lal dichlorqsilaue which comprises forming a mixture of raq ylen i .a y ditml m e an tlrbser y .phosphonate, heating.v said .mixture to a temperature .of from about 125 C. to about 300 C. to'cause ,acrylonitrile and alkyldichlorosilane to react to;.pro- .duce a beta cyanoethylalkyldichlorosilane.

14. A process for producing a .beta-cyanoethylaryldichlorosilanervhich comprises forming a mixture of acrylonitrile, aryldichlorosilane and a .hydrocarbyl phosphonate, heating said mixture to a temperature of f rom about 1 25 C to about 300 C. to causesaidfsilaneand acryloniti-ile toreact to produce a betacyanoethylaryldichlorosilane. l i

15. A process for reacting a silane, represented by the formula:

where E.represents amember of the group consisting of hydrogen and a hydrocarbyl group, X represents a hydrolyzable groupfrom the class consisting of-halogenand ,hydrocarbyloxygroups and n represents a whole number having a ,valueof from 0 to 2, with an alkene nitn'le .to produce a cyanoalkylsilane by the addition of a silyl g Oup-tothe olefinic carbon atom of said alkene nitrile ,further removed from the cyano group't hereofand by .the,addition of a hydrogen atom to the olefinic carbon atomof said alkene nitrile closer to the cyano group jthereofwvhich comprises forming a mixture of ,said silane,

.said alkene nitrile, and a hydrocarbyl Pl' osphonate catalyst within a closed system, heating .sa id mixtureto a temperature sufiiciently elevated to cause said silane and nitrile to react to produce a cyanoalkylsilane by the addition to 21v silyl group .to the olefinic carbon 1 atom rfurther rem'ovedirom-the cyano group of thestartingnitrileand by theaddition of ahydrogen atom to the olefinic carbon atomclosentothe cyano group of the starting nitrile.

LRefer-encesCited in the file of this patent UNITED .STATES PATENTS 2,721,873 McKenzie et al. .Oct. 25, 1955 

1. A PROCESS FOR REACTING A SILANE, REPRESENTED BY THE FORMULA: 